Zeolites are a class of important materials used in the chemical industry for processes such as gas stream purification and hydrocarbon conversion processes. Zeolites are porous solids having interconnected pores of different sizes. Zeolites typically have a one-, two- or three-dimensional crystalline pore structure having pores of one or more molecular dimensions that selectively adsorb molecules that can enter the pores, and exclude those molecules that are too large. The pore size, pore shape, interstitial spacing or channels, composition, crystal morphology and structure are a few characteristics of zeolites that determine their use in various adsorption and hydrocarbon conversion processes.
Molecular sieves identified by the International Zeolite Associate (IZA) as having the structure code MWW are known. For example, the molecular sieve known as SSZ-25 is a known crystalline MWW material. It is disclosed in U.S. Pat. No. 5,202,014, issued Apr. 13, 1993 to Zones et al. In that patent, the SSZ-25 molecular sieve is prepared using a adamantane quaternary ammonium hydroxide (e.g. N,N,N-trimethyl-1-adamantanammonium hydroxide) as the structure-directing agent (SDA).
U.S. Pat. No. 4,954,325 to Chu and Rubin, published Sep. 4, 1990, discloses the preparation of MWW molecular sieve MCM-22 using hexamethyleneimine. Other known SDAs for synthesizing MCM-22 include N,N,N,N′N′N′-hexamethyl-1,5-hexanediaminium salts, N,N,N,N′N′N′-hexamethyl-1,5-pentanediaminium salts, cyclopentylamine-based SDAs, cyclohexylamine-based SDAs, cycloheptylamine-based SDAs, heptamethyleneimine-based SDAs, and homopiperazine-based SDAs, as described in U.S. Pat. No. 7,842,277 to Roth et al., issued Nov. 30, 2010, and U.S. Pat. No. 7,883,686 to Lai et al., issued Feb. 8, 2011.
However, known SDAs useful for making MWW materials are complex and typically not available in quantities necessary to produce MWW materials on a commercial scale. It has now been found that MWW-type molecular sieves can be prepared using cationic 1,3-diisobutylimidazolium as the structure directing agent.